What is the social history of the unit of observation’s definition? How do social groups talk about this definition? How has it been contested?

By reading the dataset it occured to me that in most households, different water connections are built in for different purposes already: the kitchen tap is generally used for food / drinking or washing hands, the dishwasher usually has a separate connection, all the toilet connections have a different purpose, etc. This makes distinguishing different water usecases easier, but uncertainties remain: Without a dishwasher, it is difficult to distinguish between cooking and washing hands or dishes from the kitchen tap.